This is a source incompatible change for widget implementors.
Leaving the old enterEvent as a virtual overload is problematic due to
shadowing. Best to make a clean cut, widget reimplementors will get a compile
time warning if they mark their override as such, or if they try to call the
parent class implementation.
Addresses ### Qt 6 comment.
[ChangeLog][QtWidgets][QWidget] The virtual enterEvent handler now receives
a QEnterEvent, which contains information about mouse position and button
states, rather than a plain QEvent.
Change-Id: I233f594fd79c0c090983b3db8532913d00132fde
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>